A fiber-reinforced composite (hereinafter referred to as composite) is used as a material that is lightweight and has high strength. The composite is synthesized by impregnating reinforcement fibers with a matrix resin to improve the dynamic properties (mechanical properties) as compared with when the matrix resin is used solely. Thus, the composite is used as a preferable structural component.
For example, a fiber structure serving as a reinforcement base of a composite includes a stack of a plurality of fiber layers, each of which includes an arrangement of reinforcement fiber warps or wefts, and auxiliary yarns, which join the fiber layers in the stacking direction. Further, in order to exhibit dynamic properties in directions other than the main axis directions of the warps and the wefts (directions in which yarns extend), there may be cases in which the composite includes, in addition to the warp layers and weft layers, fiber layers of bias direction yarns arranged so that the main axis direction extends in a direction that differs from main axis directions of the warps and wefts. For example, as shown in FIG. 7, a five-axis three-dimensional fabric 80 of patent document 1 includes a warp layer 81 that is an arrangement of a plurality of warps 81a, a weft layer 82 that is an arrangement of a plurality of wefts 82a, and two bias yarn layers 83 and 84. The layers are stacked and joined together by vertical yarns 85 in the stacking direction. First bias yarns 83a of one of the bias yarn layers 83 are inclined relative to the warps 81a by a fixed angle, and second bias yarns 84a of the other one of the bias yarn layers 84 are inclined relative to the warp 81a by a fixed angle in the direction opposite to the first bias yarn 83a. In the five-axis three-dimensional fabric 80, the two types of the bias yarns 83a and 84a extend in directions other than the main axis direction of the warp 81a and the main axis direction of the weft 82a. This improves the dynamic properties in the direction in which the bias yarns 83a and 84a extend.